The first molecular component involved in the pathogenesis of open-angle glaucoma has been identified. Mutations causing glaucoma in some are located to an open-angle glaucoma gene, GLC1A, on chromosome 1 that codes for a protein called myocilin. Myocilin is a novel protein of unknown function that is found in several eye tissues, including the trabecular meshwork, the likely site of pathology in open-angle glaucoma. On a subcellular level, myociin localizes to the vesicular compartment of trabecular meshwork cells, implicating vesicular traffic and/or secretion as affected pathways in open-angle glaucoma. Computer analyses of myocilin's primary sequence indicate significant homology to the SNARE [soluble N-ethylmaleimide sensitive fusion protein (NSF) attachment protein (SNAP) receptor] and Olfactomedin protein families, both of which localize to and function in the secretory pathway of cells. Moreover, preliminary data presented in this proposal indicate that 1) myocilin functions in both the formation and fusion of secretory-type vesicles in trabecular meshwork (HTM) cells and 2) myocilin-associated vesicles participate in the regulated assembly of nascent cell-cell junctions in two different epithelial cell models. Thus, the overall goal of this grant proposal is to determine the role of myocilin in the process of nascent cell-cell junction assembly in trabecular meshwork cells and the functional consequence of mutations in myocilin on this process. To this end, colocalization studies of myocilin with proteins known to participate in nascent cell-cell junctions will be performed in HTM cells. Second, the regulated targeting of myocilin to nascent cell-cell junctions in HTM cells will be studied. Finally, the functional consequence of mutations in myocilin (disease causing in humans) will be monitored using HTM cells as a model. These studies are designed to examine the molecular pathway in which myocilin functions in HTM cells. This knowledge will contribute to our understanding of glaucoma at the molecular level and provide new therapeutic targets for the treatment of those who are afflicted with glaucoma.